Hi, we are new to this forum and beekeeping. We have a hybrid nuc with 2 national frames and the rest are top bars.

Soon we will be able to transfer all the frames into the top bar hive. We understand about cutting and cropping and moving - that's not a problem.

My question is - having adapted and transferred the national frames to the top bar, if/when can or should we remove them. We don't want to leave them there permanently, if possible. Do we do this before the end of the season or wait until next year?

Ideally you need to gradually move them to the back of the hive until they are clear of the brood nest and become used for honey storage and then harvest them out. This will involve gradually inserting empty top bars between them and the rest of the brood nest until they are beyond the range of the brood nest. Placing them further away from the entrance than the top bar combs in the nuc when you transfer them into the hive will make it easier, as you need to gradually move them towards the back of the hive for honey storage.
Don't be tempted to move them to the back of the hive too soon though, because if a brood comb gets isolated from the brood nest, the nurse bees on it will try to raise an emergency queen and then things can get complicated, so just move them along and insert one bar at a time
It is likely to take a year or so to work them out of use in this way.

I hope that makes sense, but if not, say so and I'll try to explain better.

Conserving wild bees

Research suggests that bumble bee boxes have a very low success rate in actually attracting bees into them. We find that if you create an environment where first of all you can attract mice inside, such as a pile of stones, a drystone wall, paving slabs with intentionally made cavities underneath, this will increase the success rate.

Most bumble bee species need a dry space about the size a football, with a narrow entrance tunnel approximately 2cm in diameter and 20 cm long. Most species nest underground along the base of a linear feature such as a hedge or wall. Sites need to be sheltered and out of direct sunlight.